Koys was (still is) not physically build to high level like NHL. The hype came right like it is with Slafkovsky, when he was 14 years old and had such crazy numbers. But not in U 18 league, in the lower class. Then some canadian blogger made an article, where his numbers in this slow level Slovak league were compared to Crosby numbers in his age and voila, we had a star.
Slafkovsky is big body now, so he could use it to his advantage. The question is, how will it look like in 2-3 years, when he will be in the same fishpond like others big fishes.